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3.3.3 Glaciers - Biology


While ice sheets and sea ice are restricted to the poles, glaciers occur throughout the world, even in tropical locations, where mountain ranges reach elevations high enough to allow the development of ice. The World Glacier Monitoring Service (WGMS) tracks and reports data on ‘reference’ glaciers (glaciers with greater than 30 years of documented mass-balance measurements). Mass data on these reference glaciers indicates significant degrees of glacier mass loss across the globe (Fig 3.3.3.1).

Figure (PageIndex{1}): Cumulative glacier mass change for reference glaciers across the globe from 1950 to 2020 compared to each glacier’s mass value in 1976. Positive values indicate higher glacier mass, negative values indicate lower mass compared to 1976. Colored lines represent reference glaciers in different regions, while the black dotted line represents the global average across all regions. Image from WGMS 20201

In 1997, researchers at the Northern Rocky Mountain Science Center began the Repeat Photography Project to illustrate changes in glacier extent in Glacier National Park, Montana, USA through current and historical photography. The value of this project is illustrated by the highly visible change in Grinnell Glacier from 1938 to 2015 (Fig 3.3.3.2). Warming and glacier melt is so severe in this region that a 2003 study estimated that the park may be ice-free, containing not a single glacier, by the year 2030 (Hall and Fagre, 2003), though other studies have predicted some glaciers may persist as long as 2080 (Brown et al 2010).

Figure (PageIndex{1}): Ice loss in Grinnell Glacier in Glacier National Park, Montana USA. Images modified from USGS2.

Image Credits

  1. WGMS (2020, updated, and earlier reports). Global Glacier Change Bulletin No. 3 (2016-2017). Zemp, M., Gärtner-Roer, I., Nussbaumer, S. U., Bannwart, J., Rastner, P., Paul, F., and Hoelzle, M. (eds.), ISC(WDS)/IUGG(IACS)/UNEP/UNESCO/WMO, World Glacier Monitoring Service, Zurich, Switzerland, 274 pp., publication based on database version: doi:10.5904/wgms-fog-2019-12.


Subglacial lake

A subglacial lake is a lake that is found under a glacier, typically beneath an ice cap or ice sheet. Subglacial lakes form at the boundary between ice and the underlying bedrock, where gravitational pressure decreases the pressure melting point of ice. [1] [2] Over time, the overlying ice gradually melts at a rate of a few millimeters per year. [3] Meltwater flows from regions of high to low hydraulic pressure under the ice and pools, creating a body of liquid water that can be isolated from the external environment for millions of years. [1] [4]

Since the first discoveries of subglacial lakes under the Antarctic Ice Sheet, more than 400 subglacial lakes have been discovered in Antarctica, beneath the Greenland Ice Sheet, and under Iceland's Vatnajökull ice cap. [5] [6] [7] Subglacial lakes contain a substantial proportion of Earth's liquid freshwater, with the volume of Antarctic subglacial lakes alone estimated to be about 10,000 km 3 , or about 15% of all liquid freshwater on Earth. [8]

As ecosystems isolated from Earth's atmosphere, subglacial lakes are influenced by interactions between ice, water, sediments, and organisms. They contain active biological communities of extremophilic microbes that are adapted to cold, low-nutrient conditions and facilitate biogeochemical cycles independent of energy inputs from the sun. [9] Subglacial lakes and their inhabitants are of particular interest in the field of astrobiology and the search for extraterrestrial life. [10] [11]


South Carolina State Standards for Science: Grade 3

Currently Perma-Bound only has suggested titles for grades K-8 in the Science and Social Studies areas. We are working on expanding this.

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SC.3-1. Scientific Inquiry: The student will demonstrate an understanding of scientific inquiry, including the processes, skills, and mathematical thinking necessary to conduct a simple scientific investigation.

3-1.1. Classify objects by two of their properties (attributes). 5
Suggested Titles for South Carolina Science State Standard 3-1.1.

3-1.2. Classify objects or events in sequential order. 19
Suggested Titles for South Carolina Science State Standard 3-1.2.

3-1.3. Generate questions such as 'what if?' or 'how?' about objects, organisms, and events in the environment and use those questions to conduct a simple scientific investigation. 23
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3-1.4. Predict the outcome of a simple investigation and compare the result with the prediction. 23
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3-1.5. Use tools (including beakers, meter tapes and sticks, forceps/tweezers, tuning forks, graduated cylinders, and graduated syringes) safely, accurately, and appropriately when gathering specific data.

3-1.6. Infer meaning from data communicated in graphs, tables, and diagrams. 5
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3-1.7. Explain why similar investigations might produce different results. 23
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3-1.8. Use appropriate safety procedures when conducting investigations. 23
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SC.3-2. Habitats and Adaptations: The student will demonstrate an understanding of the structures, characteristics, and adaptations of organisms that allow them to function and survive within their habitats. (Life Science)

3-2.1. Illustrate the life cycles of seed plants and various animals and summarize how they grow and are adapted to conditions within their habitats. 120
Suggested Titles for South Carolina Science State Standard 3-2.1.

3-2.2. Explain how physical and behavioral adaptations allow organisms to survive (including hibernation, defense, locomotion, movement, food obtainment, and camouflage for animals and seed dispersal, color, and response to light for plants). 42
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3-2.3. Recall the characteristics of an organism's habitat that allow the organism to survive there. 54
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3-2.4. Explain how changes in the habitats of plants and animals affect their survival. 18
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3-2.5. Summarize the organization of simple food chains (including the roles of producers, consumers, and decomposers). 15
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SC.3-3. Earth's Materials and Changes: The student will demonstrate an understanding of Earth's composition and the changes that occur to the features of Earth's surface. (Earth Science)

3-3.1. Classify rocks (including sedimentary, igneous, and metamorphic) and soils (including humus, clay, sand, and silt) on the basis of their properties. 6
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3-3.2. Identify common minerals on the basis of their properties by using a minerals identification key. 9
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3-3.3. Recognize types of fossils (including molds, casts, and preserved parts of plants and animals). 31
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3-3.4. Infer ideas about Earth's early environments from fossils of plants and animals that lived long ago. 5
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3-3.5. Illustrate Earth's saltwater and freshwater features (including oceans, seas, rivers, lakes, ponds, streams, and glaciers). 20
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3-3.6. Illustrate Earth's land features (including volcanoes, mountains, valleys, canyons, caverns, and islands) by using models, pictures, diagrams, and maps. 26
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3-3.7. Exemplify Earth materials that are used as fuel, as a resource for building materials, and as a medium for growing plants. 8
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3-3.8. Illustrate changes in Earth's surface that are due to slow processes (including weathering, erosion, and deposition) and changes that are due to rapid processes (including landslides, volcanic eruptions, floods, and earthquakes). 6
Suggested Titles for South Carolina Science State Standard 3-3.8.

SC.3-4. Heat and Changes in Matter: The student will demonstrate an understanding of the changes in matter that are caused by heat.

3-4.1. Classify different forms of matter (including solids, liquids, and gases) according to their observable and measurable properties. 6
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3-4.2. Explain how water and other substances change from one state to another (including melting, freezing, condensing, boiling, and evaporating). 1
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3-4.3. Explain how heat moves easily from one object to another through direct contact in some materials (called conductors) and not so easily through other materials (called insulators). 3
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3-4.4. Identify sources of heat and exemplify ways that heat can be produced (including rubbing, burning, and using electricity). 3
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SC.3-5. Motion and Sound: The student will demonstrate an understanding of how motion and sound are affected by a push or pull on an object and the vibration of an object. (Physical Science)

3-5.1. Identify the position of an object relative to a reference point by using position terms such as 'above,' 'below,' 'inside of,' 'underneath,' or 'on top of' and a distance scale or measurement. 2
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3-5.2. Compare the motion of common objects in terms of speed and direction. 6
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3-5.3. Explain how the motion of an object is affected by the strength of a push or pull and the mass of the object. 12
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3-5.4. Explain the relationship between the motion of an object and the pull of gravity. 17
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3-5.5. Recall that vibrating objects produce sound and that vibrations can be transferred from one material to another. 8
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3-5.6. Compare the pitch and volume of different sounds. 8
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3-5.7. Recognize ways to change the volume of sounds. 8
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3-5.8. Explain how the vibration of an object affects pitch. 8
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3. Origin of Life

3.1. Phylogeny

3.1.1.1. Diagram of all ancestors (lineage)

3.1.1.1.2. LUA - last universal ansestor

3.1.1.3. Used since Charles Darwin

3.1.2. Cladogram - diagram showing all the related species

3.1.3. Cladistics - uses derived characters ONLY to classify organisms

3.2. Taxonomy

3.2.1. Kingdoms (have many species each)

3.2.1.1.1. Need host to reproduce

3.2.1.1.3. Microscopic non-cellular particles of neuclaic acid in a capsid

3.2.1.1.4. Asexual reproduction

3.2.1.2.1. Eubacteria and Archeabacteria used to be classified as bacteria, but this is outdated

3.2.1.2.2. Microscopic and everywhere

3.2.1.2.3. Simplest form of life

3.2.1.2.6. Plasmid - genes that learn to resist medicine

3.2.1.2.7. Cell wall made of peptidoglycan

3.2.1.3.3. Reproduction by spores

3.2.1.4.3. Alternating generations - one generation has gamete producing haploids and the next has spore producing diploids

3.2.1.5.3. Sexual reproduction

3.2.1.5.4. Multicellular heteratrophs

3.2.1.5.6. 0, 2 or 3 germ layers

3.2.1.5.7. Blastula - stage of embryo before gastrulation

3.2.1.5.8. Invertebrates - animal without a backbone, but replaces with and exoskeleton

3.2.1.5.9. Vertebrates - animal with a backbone or spine inside their body eubacteria found in intestines

3.2.1.5.10. Arthropod - inveterbrate with a segmented body such as insects and spider exoskeleton formed by carbohydrate called chitin

3.2.1.6.3. Has multicellularity Autotrophic

3.2.1.6.4. Tropism - respond to stimuli such as a plant moving towards sunlight

3.2.1.6.5. Transpiration - plants releasing water vapor into the air through the stromata

3.2.2. Science of naming species (plant, animal. )

3.2.2.1. Based on genetics, behavior and observations

3.2.2.2. Species have a biological difference

3.2.2.2.1. Different species cannot reproduce

3.2.2.3. Binamial naming system

3.2.2.3.1. Each species has two names

3.2.3. Genus - taxonomic rank used in classifying species

3.2.4. Phylum - classification before class and after kingdom

3.2.5. Aka evolutionary systematics

3.3. Where did life come from?

3.3.1.1. Mix of all organisms before the species and before complex life

3.3.2.1. Simulated conditions thought to be like early Earth

3.3.3. Innate Behavior - behavior that was inherited from generation to generation such as foraging, mobility and defense

3.3.3.1. Ancestral characters - characteristics that were inherited and all the of species have them

3.3.4. Learned Behaviors - behaviors that organisms have adapted to create though analogous evolution aka mutations such as migratation

3.3.4.1. Differentiation - when cells change in order to accommodate needs of an organism

3.3.5. Eukaryotes are from the eukaraya taxon

3.4. Key

3.4.1. Endosymbiosis - one organism living inside another, such as viruses living inside another organism to use a host cell

3.4.2. Domain - highest rank of taxonomic speceis

3.4.3. Ozone layer - Layer that carbon effects

3.4.4. Aggregation - cells that are affiliated with each other, meet then dispurse

3.4.5. Photoperiodism - response to changes in day length such as getting tired (plants and animals)

3.4.6. Colonial organism - identical cells that have no interaction inside of the cell, however are associated together

3.4.7. Cephalization - Tissues that enable organisms to move such as the brain and head


Key Facts & Information

Summary:

  • Addition of numbers means to find the total value or sum of those numbers combined.
    Example: 1 + 6 = 7
  • Repeated addition means to add a number over and over.
    Example: 2 + 2 + 2 + 2 = 8
  • Repeated additions helps form a strong base for multiplication.

What is addition?

  • Addition is a mathematical operation.
  • When we add numbers, we find their combined value. Addition is an integral part of mathematics and serves as foundation for understanding other operations.
  • The symbol used for this operation is “+”.
  • Here we will give simple examples of single digit addition:

Repeated addition

  • In this specific form of addition what we do is we add the same number over and over. It acts as a foundation for learning multiplication.
  • In multiplication we add same sized group many times. In repeated addition we do the same.
  • When children are familiar with repeated addition, it will not be difficult for them to understand the concept of multiplication.
  • Here we will explain this concept with the help of an example and show how it is related to multiplication. Suppose we add 3 four times as shown below:

  • So when we add four groups of three we will get 12.
  • Similarly when we say we multiply 3 by 4 it also means that we are adding four groups of three.
  • This is why learning repeated addition is very important. Students that have a firm grip on repeated addition find it much easier to understand multiplication.
  • Now suppose we add 4 two times:

  • When we add two groups of four we get 8. Similarly we can also say we are multiplying 4 by 2.
  • Hence we can use repeated addition to add as many groups as we want.

Example:

  • We see that we have four groups of two apples each.
  • So we can say that we are adding 2 four times.
  • This is explained by the equation given below.

2 + 2 + 2 + 2 = 8
total apples = 8

Example:

  • We see that we have eight groups of three bananas each. So will use repeated addition to add 3 eight times.

3 + 3 +3 + 3 + 3 + 3 + 3 + 3 = 24
total bananas = 24

Example:

We can use repeated addition to find total number of ears of four sheeps.
total ears = 2 + 2 + 2 + 2
total ears = 8

We can use repeated addition to find total number of legs of four sheeps.
total legs = 4 + 4 + 4 + 4
total legs = 16

Example:

  • Hannah has three beautiful baskets. Each basket is filled with goodies. She wants to distribute theses goodies to the children in her class. Each basket has six goodies.
  • How many goodies does each basket have ?
    Each basket has 6 goodies.
  • What is the total number of goodies ?

We use repeated addition to find the total number of goodies. We know that there are six baskets in total and each basket has six goodies so total number of goodies can be calculated as follows:
total goodies = 6 + 6 + 6
total goodies = 18
So we can say she has 3 groups of 6 goodies.

  • If total number of student in her class in 9, how many goodies can she give each student so that all 18 goodies are distributed. She has to make sure all class fellows get equal number of goodies.

We know that total number of students is 9 so we give each student one goodie. After giving 9 goodies we see that 9 goodies are still left. So we distribute the remaining 9 among the 9 students. So each students gets two goodies. We can say we have nine groups of two goodies as show below:

2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 = 18

We can also solve this using multiplication by using the following equation:
9 x 2 = 18

Repeated Addition Worksheets

This is a fantastic bundle which includes everything you need to know about repeated addition across 28 in-depth pages. These are ready-to-use Repeated Addition worksheets that are perfect for teaching students about the repeated additions which helps form a strong base for multiplication. In this specific form of addition what we do is we add the same number over and over. In multiplication we add same sized group many times. In repeated addition we do the same.

Complete List Of Included Worksheets

  • Worksheet 1 (Beginner)
  • Worksheet 2 (Beginner)
  • Worksheet 3 (Beginner)
  • Worksheet 4 (Beginner
  • Worksheet 5 (Intermediate)
  • Worksheet 6 (Intermediate)
  • Worksheet 7 (Intermediate)
  • Worksheet 8 (Intermediate)
  • Worksheet 9 (Advance)
  • Worksheet 10 (Advance)
  • Worksheet 11 (Advance)
  • Worksheet 12 (Advance)

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Use With Any Curriculum

These worksheets have been specifically designed for use with any international curriculum. You can use these worksheets as-is, or edit them using Google Slides to make them more specific to your own student ability levels and curriculum standards.


Contents

The word deer was originally broad in meaning, becoming more specific with time. Old English dēor and Middle English der meant a wild animal of any kind. Cognates of Old English dēor in other dead Germanic languages have the general sense of animal, such as Old High German tior, Old Norse djur or dȳr, Gothic dius, Old Saxon dier, and Old Frisian diar. [3] This general sense gave way to the modern English sense by the end of the Middle English period, around 1500. All modern Germanic languages save English and Scots retain the more general sense: for example, German Tier and Norwegian dyr mean animal. [4]

For many types of deer in modern English usage, the male is a buck and the female a doe, but the terms vary with dialect, and according to the size of the species. The male red deer is a stag, while for other large species the male is a bull, the female a cow, as in cattle. In older usage, the male of any species is a hart, especially if over five years old, and the female is a hind, especially if three or more years old. [5] The young of small species is a fawn and of large species a calf a very small young may be a kid. A castrated male is a havier. [6] A group of any species is a herd. The adjective of relation is cervine like the family name Cervidae, this is from Latin: cervus, meaning stag or deer.

Deer live in a variety of biomes, ranging from tundra to the tropical rainforest. While often associated with forests, many deer are ecotone species that live in transitional areas between forests and thickets (for cover) and prairie and savanna (open space). The majority of large deer species inhabit temperate mixed deciduous forest, mountain mixed coniferous forest, tropical seasonal/dry forest, and savanna habitats around the world. Clearing open areas within forests to some extent may actually benefit deer populations by exposing the understory and allowing the types of grasses, weeds, and herbs to grow that deer like to eat. Access to adjacent croplands may also benefit deer. Adequate forest or brush cover must still be provided for populations to grow and thrive.

Deer are widely distributed, with indigenous representatives in all continents except Antarctica and Australia, though Africa has only one native deer, the Barbary stag, a subspecies of red deer that is confined to the Atlas Mountains in the northwest of the continent. Another extinct species of deer, Megaceroides algericus, was present in North Africa until 6000 years ago. Fallow deer have been introduced to South Africa. Small species of brocket deer and pudús of Central and South America, and muntjacs of Asia generally occupy dense forests and are less often seen in open spaces, with the possible exception of the Indian muntjac. There are also several species of deer that are highly specialized and live almost exclusively in mountains, grasslands, swamps, and "wet" savannas, or riparian corridors surrounded by deserts. Some deer have a circumpolar distribution in both North America and Eurasia. Examples include the caribou that live in Arctic tundra and taiga (boreal forests) and moose that inhabit taiga and adjacent areas. Huemul deer (taruca and Chilean huemul) of South America's Andes fill the ecological niches of the ibex and wild goat, with the fawns behaving more like goat kids.

The highest concentration of large deer species in temperate North America lies in the Canadian Rocky Mountain and Columbia Mountain regions between Alberta and British Columbia where all five North American deer species (white-tailed deer, mule deer, caribou, elk, and moose) can be found. This region has several clusters of national parks including Mount Revelstoke National Park, Glacier National Park (Canada), Yoho National Park, and Kootenay National Park on the British Columbia side, and Banff National Park, Jasper National Park, and Glacier National Park (U.S.) on the Alberta and Montana sides. Mountain slope habitats vary from moist coniferous/mixed forested habitats to dry subalpine/pine forests with alpine meadows higher up. The foothills and river valleys between the mountain ranges provide a mosaic of cropland and deciduous parklands. The rare woodland caribou have the most restricted range living at higher altitudes in the subalpine meadows and alpine tundra areas of some of the mountain ranges. Elk and mule deer both migrate between the alpine meadows and lower coniferous forests and tend to be most common in this region. Elk also inhabit river valley bottomlands, which they share with White-tailed deer. The White-tailed deer have recently expanded their range within the foothills and river valley bottoms of the Canadian Rockies owing to conversion of land to cropland and the clearing of coniferous forests allowing more deciduous vegetation to grow up the mountain slopes. They also live in the aspen parklands north of Calgary and Edmonton, where they share habitat with the moose. The adjacent Great Plains grassland habitats are left to herds of elk, American bison, and pronghorn.

The Eurasian Continent (including the Indian Subcontinent) boasts the most species of deer in the world, with most species being found in Asia. Europe, in comparison, has lower diversity in plant and animal species. Many national parks and protected reserves in Europe have populations of red deer, roe deer, and fallow deer. These species have long been associated with the continent of Europe, but also inhabit Asia Minor, the Caucasus Mountains, and Northwestern Iran. "European" fallow deer historically lived over much of Europe during the Ice Ages, but afterwards became restricted primarily to the Anatolian Peninsula, in present-day Turkey.

Present-day fallow deer populations in Europe are a result of historic man-made introductions of this species, first to the Mediterranean regions of Europe, then eventually to the rest of Europe. They were initially park animals that later escaped and reestablished themselves in the wild. Historically, Europe's deer species shared their deciduous forest habitat with other herbivores, such as the extinct tarpan (forest horse), extinct aurochs (forest ox), and the endangered wisent (European bison). Good places to see deer in Europe include the Scottish Highlands, the Austrian Alps, the wetlands between Austria, Hungary, and the Czech Republic and some fine National Parks, including Doñana National Park in Spain, the Veluwe in the Netherlands, the Ardennes in Belgium, and Białowieża National Park of Poland. Spain, Eastern Europe, and the Caucasus Mountains still have virgin forest areas that are not only home to sizable deer populations but also for other animals that were once abundant such as the wisent, Eurasian lynx, Iberian lynx, wolves, and brown bears.

The highest concentration of large deer species in temperate Asia occurs in the mixed deciduous forests, mountain coniferous forests, and taiga bordering North Korea, Manchuria (Northeastern China), and the Ussuri Region (Russia). These are among some of the richest deciduous and coniferous forests in the world where one can find Siberian roe deer, sika deer, elk, and moose. Asian caribou occupy the northern fringes of this region along the Sino-Russian border.

Deer such as the sika deer, Thorold's deer, Central Asian red deer, and elk have historically been farmed for their antlers by Han Chinese, Turkic peoples, Tungusic peoples, Mongolians, and Koreans. Like the Sami people of Finland and Scandinavia, the Tungusic peoples, Mongolians, and Turkic peoples of Southern Siberia, Northern Mongolia, and the Ussuri Region have also taken to raising semi-domesticated herds of Asian caribou.

The highest concentration of large deer species in the tropics occurs in Southern Asia in India's Indo-Gangetic Plain Region and Nepal's Terai Region. These fertile plains consist of tropical seasonal moist deciduous, dry deciduous forests, and both dry and wet savannas that are home to chital, hog deer, barasingha, Indian sambar, and Indian muntjac. Grazing species such as the endangered barasingha and very common chital are gregarious and live in large herds. Indian sambar can be gregarious but are usually solitary or live in smaller herds. Hog deer are solitary and have lower densities than Indian muntjac. Deer can be seen in several national parks in India, Nepal, and Sri Lanka of which Kanha National Park, Dudhwa National Park, and Chitwan National Park are most famous. Sri Lanka's Wilpattu National Park and Yala National Park have large herds of Indian sambar and chital. The Indian sambar are more gregarious in Sri Lanka than other parts of their range and tend to form larger herds than elsewhere.

The Chao Praya River Valley of Thailand was once primarily tropical seasonal moist deciduous forest and wet savanna that hosted populations of hog deer, the now-extinct Schomburgk's deer, Eld's deer, Indian sambar, and Indian muntjac. Both the hog deer and Eld's deer are rare, whereas Indian sambar and Indian muntjac thrive in protected national parks, such as Khao Yai. Many of these South Asian and Southeast Asian deer species also share their habitat with other herbivores, such as Asian elephants, the various Asian rhinoceros species, various antelope species (such as nilgai, four-horned antelope, blackbuck, and Indian gazelle in India), and wild oxen (such as wild Asian water buffalo, gaur, banteng, and kouprey). One way that different herbivores can survive together in a given area is for each species to have different food preferences, although there may be some overlap.

Australia has six introduced species of deer that have established sustainable wild populations from acclimatisation society releases in the 19th century. These are the fallow deer, red deer, sambar, hog deer, rusa, and chital. Red deer introduced into New Zealand in 1851 from English and Scottish stock were domesticated in deer farms by the late 1960s and are common farm animals there now. Seven other species of deer were introduced into New Zealand but none are as widespread as red deer. [7]

Deer constitute the second most diverse family of artiodactyla after bovids. [8] Though of a similar build, deer are strongly distinguished from antelopes by their antlers, which are temporary and regularly regrown unlike the permanent horns of bovids. [9] Characteristics typical of deer include long, powerful legs, a diminutive tail and long ears. [10] Deer exhibit a broad variation in physical proportions. The largest extant deer is the moose, which is nearly 2.6 metres (8.5 ft) tall and weighs up to 800 kilograms (1,800 lb). [11] [12] The elk stands 1.4–2 metres (4.6–6.6 ft) at the shoulder and weighs 240–450 kilograms (530–990 lb). [13] The northern pudu is the smallest deer in the world it reaches merely 32–35 centimetres (13–14 in) at the shoulder and weighs 3.3–6 kilograms (7.3–13.2 lb). The southern pudu is only slightly taller and heavier. [14] Sexual dimorphism is quite pronounced – in most species males tend to be larger than females, [15] and, except for the reindeer, only males possess antlers. [16]

Coat colour generally varies between red and brown, [17] though it can be as dark as chocolate brown in the tufted deer [18] or have a grayish tinge as in elk. [13] Different species of brocket deer vary from gray to reddish brown in coat colour. [19] Several species such as the chital, [20] the fallow deer [21] and the sika deer [22] feature white spots on a brown coat. Coat of reindeer shows notable geographical variation. [23] Deer undergo two moults in a year [17] [24] for instance, in red deer the red, thin-haired summer coat is gradually replaced by the dense, greyish brown winter coat in autumn, which in turn gives way to the summer coat in the following spring. [25] Moulting is affected by the photoperiod. [26]

Deer are also excellent jumpers and swimmers. Deer are ruminants, or cud-chewers, and have a four-chambered stomach. Some deer, such as those on the island of Rùm, [27] do consume meat when it is available. [28]

Nearly all deer have a facial gland in front of each eye. The gland contains a strongly scented pheromone, used to mark its home range. Bucks of a wide range of species open these glands wide when angry or excited. All deer have a liver without a gallbladder. Deer also have a tapetum lucidum, which gives them sufficiently good night vision.

Antlers Edit

All male deer possess antlers, with the exception of the water deer, in which males have long tusk-like canines that reach below the lower jaw. [29] Females generally lack antlers, though female reindeer bear antlers smaller and less branched than those of the males. [30] Occasionally females in other species may develop antlers, especially in telemetacarpal deer such as European roe deer, red deer, white-tailed deer and mule deer and less often in plesiometacarpal deer. A study of antlered female white-tailed deer noted that antlers tend to be small and malformed, and are shed frequently around the time of parturition. [31]

The fallow deer and the various subspecies of the reindeer have the largest as well as the heaviest antlers, both in absolute terms as well as in proportion to body mass (an average of 8 grams (0.28 oz) per kilogram of body mass) [30] [32] the tufted deer, on the other hand, has the smallest antlers of all deer, while the pudú has the lightest antlers with respect to body mass (0.6 grams (0.021 oz) per kilogram of body mass). [30] The structure of antlers show considerable variation while fallow deer and elk antlers are palmate (with a broad central portion), white-tailed deer antlers include a series of tines sprouting upward from a forward-curving main beam, and those of the pudú are mere spikes. [14] Antler development begins from the pedicel, a bony structure that appears on the top of the skull by the time the animal is a year old. The pedicel gives rise to a spiky antler the following year, that is replaced by a branched antler in the third year. This process of losing a set of antlers to develop a larger and more branched set continues for the rest of the life. [30] The antlers emerge as soft tissues (known as velvet antlers) and progressively harden into bony structures (known as hard antlers), following mineralisation and blockage of blood vessels in the tissue, from the tip to the base. [33]

Antlers might be one of the most exaggerated male secondary sexual characteristics, [34] and are intended primarily for reproductive success through sexual selection and for combat. The tines (forks) on the antlers create grooves that allow another male's antlers to lock into place. This allows the males to wrestle without risking injury to the face. [35] Antlers are correlated to an individual's position in the social hierarchy and its behaviour. For instance, the heavier the antlers, the higher the individual's status in the social hierarchy, and the greater the delay in shedding the antlers [30] males with larger antlers tend to be more aggressive and dominant over others. [36] Antlers can be an honest signal of genetic quality males with larger antlers relative to body size tend to have increased resistance to pathogens [37] and higher reproductive capacity. [38]

In elk in Yellowstone National Park, antlers also provide protection against predation by wolves. [39]

Homology of tines, that is, the branching structure of antlers among species, have been discussed before the 1900s. [40] [41] [42] Recently, a new method to describe the branching structure of antlers and determining homology of tines was developed. [43]

Teeth Edit

Most deer bear 32 teeth the corresponding dental formula is: 0.0.3.3 3.1.3.3 . The elk and the reindeer may be exceptions, as they may retain their upper canines and thus have 34 teeth (dental formula: 0.1.3.3 3.1.3.3 ). [44] The Chinese water deer, tufted deer, and muntjac have enlarged upper canine teeth forming sharp tusks, while other species often lack upper canines altogether. The cheek teeth of deer have crescent ridges of enamel, which enable them to grind a wide variety of vegetation. [45] The teeth of deer are adapted to feeding on vegetation, and like other ruminants, they lack upper incisors, instead having a tough pad at the front of their upper jaw.

Diet Edit

Deer are browsers, and feed primarily on foliage of grasses, sedges, forbs, shrubs and trees, secondarily on lichens in northern latitudes during winter. [46] They have small, unspecialized stomachs by ruminant standards, and high nutrition requirements. Rather than eating and digesting vast quantities of low-grade fibrous food as, for example, sheep and cattle do, deer select easily digestible shoots, young leaves, fresh grasses, soft twigs, fruit, fungi, and lichens. The low-fibered food, after minimal fermentation and shredding, passes rapidly through the alimentary canal. The deer require a large amount of minerals such as calcium and phosphate in order to support antler growth, and this further necessitates a nutrient-rich diet. There are some reports of deer engaging in carnivorous activity, such as eating dead alewives along lakeshores [47] or depredating the nests of northern bobwhites. [48]

Reproduction Edit

Nearly all cervids are so-called uniparental species: the fawns are only cared for by the mother, known as a doe. A doe generally has one or two fawns at a time (triplets, while not unknown, are uncommon). Mating season typically begins in later August and lasts until December. Some species mate until early March. The gestation period is anywhere up to ten months for the European roe deer. Most fawns are born with their fur covered with white spots, though in many species they lose these spots by the end of their first winter. In the first twenty minutes of a fawn's life, the fawn begins to take its first steps. Its mother licks it clean until it is almost free of scent, so predators will not find it. Its mother leaves often to graze, and the fawn does not like to be left behind. Sometimes its mother must gently push it down with her foot. [49] [ better source needed ] The fawn stays hidden in the grass for one week until it is strong enough to walk with its mother. The fawn and its mother stay together for about one year. A male usually leaves and never sees his mother again, but females sometimes come back with their own fawns and form small herds.

Disease Edit

In some areas of the UK, deer (especially fallow deer due to their gregarious behaviour) have been implicated as a possible reservoir for transmission of bovine tuberculosis, [50] [51] a disease which in the UK in 2005 cost £90 million in attempts to eradicate. [52] In New Zealand, deer are thought to be important as vectors picking up M. bovis in areas where brushtail possums Trichosurus vulpecula are infected, and transferring it to previously uninfected possums when their carcasses are scavenged elsewhere. [53] The white-tailed deer Odocoileus virginianus has been confirmed as the sole maintenance host in the Michigan outbreak of bovine tuberculosis which remains a significant barrier to the US nationwide eradication of the disease in livestock. [54]

Docile moose may suffer from brain worm, a helminth which drills holes through the brain in its search for a suitable place to lay its eggs. A government biologist states that "They move around looking for the right spot and never really find it." Deer appear to be immune to this parasite it passes through the digestive system and is excreted in the feces. The parasite is not screened by the moose intestine, and passes into the brain where damage is done that is externally apparent, both in behaviour and in gait. [55]

Deer, elk and moose in North America may suffer from chronic wasting disease, which was identified at a Colorado laboratory in the 1960s and is believed to be a prion disease. Out of an abundance of caution hunters are advised to avoid contact with specified risk material (SRM) such as the brain, spinal column or lymph nodes. Deboning the meat when butchering and sanitizing the knives and other tools used to butcher are amongst other government recommendations. [56]

Deer are believed to have evolved from antlerless, tusked ancestors that resembled modern duikers and diminutive deer in the early Eocene, and gradually developed into the first antlered cervoids (the superfamily of cervids and related extinct families) in the Miocene. Eventually, with the development of antlers, the tusks as well as the upper incisors disappeared. Thus, evolution of deer took nearly 30 million years. Biologist Valerius Geist suggests evolution to have occurred in stages. There are not many prominent fossils to trace this evolution, but only fragments of skeletons and antlers that might be easily confused with false antlers of non-cervid species. [14] [57]

Eocene Edit

The ruminants, ancestors of the Cervidae, are believed to have evolved from Diacodexis, the earliest known artiodactyl (even-toed ungulate), 50–55 Mya in the Eocene. [58] Diacodexis, nearly the size of a rabbit, featured the talus bone characteristic of all modern even-toed ungulates. This ancestor and its relatives occurred throughout North America and Eurasia, but were on the decline by at least 46 Mya. [58] [59] Analysis of a nearly complete skeleton of Diacodexis discovered in 1982 gave rise to speculation that this ancestor could be closer to the non-ruminants than the ruminants. [60] Andromeryx is another prominent prehistoric ruminant, but appears to be closer to the tragulids. [61]

Oligocene Edit

The formation of the Himalayas and the Alps brought about significant geographic changes. This was the chief reason behind the extensive diversification of deer-like forms and the emergence of cervids from the Oligocene to the early Pliocene. [62] The latter half of the Oligocene (28–34 Mya) saw the appearance of the European Eumeryx and the North American Leptomeryx. The latter resembled modern-day bovids and cervids in dental morphology (for instance, it had brachyodont molars), while the former was more advanced. [63] Other deer-like forms included the North American Blastomeryx and the European Dremotherium these sabre-toothed animals are believed to have been the direct ancestors of all modern antlered deer, though they themselves lacked antlers. [64] Another contemporaneous form was the four-horned protoceratid Protoceras, that was replaced by Syndyoceras in the Miocene these animals were unique in having a horn on the nose. [57] Late Eocene fossils dated approximately 35 million years ago, which were found in North America, show that Syndyoceras had bony skull outgrowths that resembled non-deciduous antlers. [65]

Miocene Edit

Fossil evidence suggests that the earliest members of the superfamily Cervoidea appeared in Eurasia in the Miocene. Dicrocerus, Euprox and Heteroprox were probably the first antlered cervids. [66] Dicrocerus featured single-forked antlers that were shed regularly. [67] Stephanocemas had more developed and diffuse ("crowned") antlers. [68] Procervulus (Palaeomerycidae) also possessed antlers that were not shed. [69] Contemporary forms such as the merycodontines eventually gave rise to the modern pronghorn. [70]

The Cervinae emerged as the first group of extant cervids around 7–9 Mya, during the late Miocene in central Asia. The tribe Muntiacini made its appearance as † Muntiacus leilaoensis around 7–8 Mya [71] The early muntjacs varied in size–as small as hares or as large as fallow deer. They had tusks for fighting and antlers for defence. [14] Capreolinae followed soon after Alceini appeared 6.4–8.4 Mya. [72] Around this period, the Tethys Ocean disappeared to give way to vast stretches of grassland these provided the deer with abundant protein-rich vegetation that led to the development of ornamental antlers and allowed populations to flourish and colonise areas. [14] [62] As antlers had become pronounced, the canines were no more retained or were poorly represented (as in elk), probably because diet was no more browse-dominated and antlers were better display organs. In muntjac and tufted deer, the antlers as well as the canines are small. The tragulids possess long canines to this day. [59]

Pliocene Edit

With the onset of the Pliocene, the global climate became cooler. A fall in the sea-level led to massive glaciation consequently, grasslands abounded in nutritious forage. Thus a new spurt in deer populations ensued. [14] [62] The oldest member of Cervini, † Cervocerus novorossiae, appeared around the transition from Miocene to Pliocene (4.2–6 Mya) in Eurasia [73] cervine fossils from early Pliocene to as late as the Pleistocene have been excavated in China [74] and the Himalayas. [75] While Cervus and Dama appeared nearly 3 Mya, Axis emerged during the late Pliocene–Pleistocene. The tribes Capreolini and Rangiferini appeared around 4–7 Mya. [72]

Around 5 Mya, the rangiferina † Bretzia and † Eocoileus were the first cervids to reach North America. [72] This implies the Bering Strait could be crossed during the late Miocene–Pliocene this appears highly probable as the camelids migrated into Asia from North America around the same time. [76] Deer invaded South America in the late Pliocene (2.5–3 Mya) as part of the Great American Interchange, thanks to the recently formed Isthmus of Panama, and emerged successful due to the small number of competing ruminants in the continent. [77]

Pleistocene Edit

Large deer with impressive antlers evolved during the early Pleistocene, probably as a result of abundant resources to drive evolution. [14] The early Pleistocene cervid † Eucladoceros was comparable in size to the modern elk. [78] † Megaloceros (Pliocene–Pleistocene) featured the Irish elk (M. giganteus), one of the largest known cervids. The Irish elk reached 2 metres (6.6 ft) at the shoulder and had heavy antlers that spanned 3.6 metres (12 ft) from tip to tip. [79] These large animals are thought to have faced extinction due to conflict between sexual selection for large antlers and body and natural selection for a smaller form. [80] Meanwhile, the moose and reindeer radiated into North America from Siberia. [81]

Deer constitute the artiodactyl family Cervidae. This family was first described by German zoologist Georg August Goldfuss in Handbuch der Zoologie (1820). Three subfamilies are recognised: Capreolinae (first described by the English zoologist Joshua Brookes in 1828), Cervinae (described by Goldfuss) and Hydropotinae (first described by French zoologist Édouard Louis Trouessart in 1898). [8] [82]

Other attempts at the classification of deer have been based on morphological and genetic differences. [57] The Anglo-Irish naturalist Victor Brooke suggested in 1878 that deer could be bifurcated into two classes on the according to the features of the second and fifth metacarpal bones of their forelimbs: Plesiometacarpalia (most Old World deer) and Telemetacarpalia (most New World deer). He treated the musk deer as a cervid, placing it under Telemetacarpalia. While the telemetacarpal deer showed only those elements located far from the joint, the plesiometacarpal deer retained the elements closer to the joint as well. [83] Differentiation on the basis of diploid number of chromosomes in the late 20th century has been flawed by several inconsistencies. [57]

In 1987, the zoologists Colin Groves and Peter Grubb identified three subfamilies: Cervinae, Hydropotinae and Odocoileinae they noted that the hydropotines lack antlers, and the other two subfamilies differ in their skeletal morphology. [84] They reverted from this classification in 2000. [85]

External relationships Edit

Until 2003, it was understood that the family Moschidae (musk deer) was sister to Cervidae. Then a phylogenetic study by Alexandre Hassanin (of National Museum of Natural History, France) and colleagues, based on mitochondrial and nuclear analyses, revealed that Moschidae and Bovidae form a clade sister to Cervidae. According to the study, Cervidae diverged from the Bovidae-Moschidae clade 27 to 28 million years ago. [86] The following cladogram is based on the 2003 study. [86]

Internal relationships Edit

A 2006 phylogenetic study of the internal relationships in Cervidae by Clément Gilbert and colleagues divided the family into two major clades: Capreolinae (telemetacarpal or New World deer) and Cervinae (plesiometacarpal or Old World deer). Studies in the late 20th century suggested a similar bifurcation in the family. This as well as previous studies support monophyly in Cervinae, while Capreolinae appears paraphyletic. The 2006 study identified two lineages in Cervinae, Cervini (comprising the genera Axis, Cervus, Dama and Rucervus) and Muntiacini (Muntiacus and Elaphodus). Capreolinae featured three lineages, Alceini (Alces species), Capreolini (Capreolus and the subfamily Hydropotinae) and Rangiferini (Blastocerus, Hippocamelus, Mazama, Odocoileus, Pudu and Rangifer species). The following cladogram is based on the 2006 study. [72]


Contents

Timeline of glaciations, shown in blue.

Ice age map of northern Germany and its northern neighbours. Red: maximum limit of Weichselian glacial yellow: Saale glacial at maximum (Drenthe stage) blue: Elster glacial maximum glaciation.

Sediment records showing the fluctuating sequences of glacials and interglacials during the last several million years.

There have been at least five major ice ages in the Earth's history (the Huronian, Cryogenian, Andean-Saharan, late Paleozoic, and the latest Quaternary Ice Age). Outside these ages, the Earth seems to have been ice free even in high latitudes.

Rocks from the earliest well established ice age, called the Huronian, formed around 2.4 to 2.1 Ga (billion years) ago during the early Proterozoic Eon. Several hundreds of km of the Huronian Supergroup are exposed 10–100 km north of the north shore of Lake Huron extending from near Sault Ste. Marie to Sudbury, northeast of Lake Huron, with giant layers of now-lithified till beds, dropstones, varves, outwash, and scoured basement rocks. Correlative Huronian deposits have been found near Marquette, Michigan, and correlation has been made with Paleoproterozoic glacial deposits from Western Australia. The Huronian ice age was caused by the elimination of atmospheric methane, a greenhouse gas, during the Great Oxygenation Event.

The next well-documented ice age, and probably the most severe of the last billion years, occurred from 720 to 630 million years ago (the Cryogenian period) and may have produced a Snowball Earth in which glacial ice sheets reached the equator, possibly being ended by the accumulation of greenhouse gases such as CO2 produced by volcanoes. "The presence of ice on the continents and pack ice on the oceans would inhibit both silicate weathering and photosynthesis, which are the two major sinks for CO2 at present." It has been suggested that the end of this ice age was responsible for the subsequent Ediacaran and Cambrian explosion, though this model is recent and controversial.

The Andean-Saharan occurred from 460 to 420 million years ago, during the Late Ordovician and the Silurian period.

The evolution of land plants at the onset of the Devonian period caused a long term increase in planetary oxygen levels and reduction of CO2 levels, which resulted in the late Paleozoic icehouse. Its former name, the Karoo glaciation, was named after the glacial tills found in the Karoo region of South Africa. There were extensive polar ice caps at intervals from 360 to 260 million years ago in South Africa during the Carboniferous and early Permian Periods. Correlatives are known from Argentina, also in the center of the ancient supercontinent Gondwanaland.

The icing of Antarctica began in the middle Eocene about 45.5 million years ago and escalated during the Eocene–Oligocene extinction event about 34 million years ago. CO2 levels were then about 760 ppm. The opening of the Drake Passage may have played a role. See Chesapeake Bay impact crater 40 km (25 mi), and Popigai crater 100 km (62 mi).

The Quaternary Glaciation / Quaternary Ice Age started about 2.58 million years ago at the beginning of the Quaternary Period when the spread of ice sheets in the Northern Hemisphere began. Since then, the world has seen cycles of glaciation with ice sheets advancing and retreating on 40,000- and 100,000-year time scales called glacial periods, glacials or glacial advances, and interglacial periods, interglacials or glacial retreats. The earth is currently in an interglacial, and the last glacial period ended about 10,000 years ago. All that remains of the continental ice sheets are the Greenland and Antarctic ice sheets and smaller glaciers such as on Baffin Island.

The definition of the Quaternary as beginning 2.58 Ma is based on the formation of the Arctic ice cap. The Antarctic ice sheet began to form earlier, at about 34 Ma, in the mid-Cenozoic (Eocene-Oligocene Boundary). The term Late Cenozoic Ice Age is used to include this early phase.

Ice ages can be further divided by location and time for example, the names Riss (180,000–130,000 years bp) and Würm (70,000–10,000 years bp) refer specifically to glaciation in the Alpine region. The maximum extent of the ice is not maintained for the full interval. The scouring action of each glaciation tends to remove most of the evidence of prior ice sheets almost completely, except in regions where the later sheet does not achieve full coverage.


Psychrophiles and Psychrotrophs

Craig L. Moyer , . Richard Y. Morita , in Reference Module in Life Sciences , 2017

The Cold Environment

Most of the Earth’s biosphere is cold. Approximately 14% of the Earth’s surface is in the polar region, whereas 71% is marine. By volume, more than 90% of the ocean is 5°C or colder. Below the thermocline, the ocean maintains a constant temperature of at most 4–5°C, regardless of latitude. Therefore, pressure-loving marine microorganisms (i.e., barophiles or more correctly known as piezophiles) are also primarily either psychrophilic or psychrotrophic ( Yayanos, 1986 Kato, 2012 ) and this is to be expected because the water below the thermocline of the ocean is under great hydrostatic pressure. In addition, the higher atmosphere is cold, hence the higher altitudes of mountain environments are also cold. The average temperature of the Earth is currently

15°C. Although the Earth is predominantly cold, the amount of research on psychrophiles is very small compared to the research on other types of extremophiles. It is important to take environmental samples where the in situ temperature never exceeds the psychrophilic range and to ensure that the medium, pipettes, inoculating loops, etc. are kept cold before use. The lack of temperature controls was probably the main reason why early microbiologists, never realizing their abnormal temperature sensitivity, failed to isolate psychrophiles. With renewed interest in life in outer space, there is a renewed interest in microorganisms that live in extreme environments, especially the cold environment.

Psychrotrophs are found in the same cold environments as psychrophiles but in greater numbers. They can also be found in cold environments which fluctuate above the psychrophilic range, mainly due to the seasonal variation in the radiant energy from the sun. Thus, ice surfaces in either northern or southern polar regions attain temperatures as high as

28°C. Psychrophiles are not present in these temperature-fluctuating environments. If the concept that either thermophiles or mesophiles were the first microorganisms to evolve on Earth, then it would follow that psychrophiles evolved from the psychrotrophs ( Morita and Moyer, 2001 ). Since the volume of the sea below the thermocline is permanently cold, it is only logical that some of the psychrophiles are also piezophiles. These extremophiles are truly multifaceted, in that in addition to pressure, they are often also tolerant to other extreme environmental forcing functions such as high salt concentrations (i.e., halophiles), ultraviolet radiation, and can survive low nutrient and water availability.

The presence of psychrophilic and psychrotrophic bacteria in cold environments (including permafrost and sea ice) permits the essential process of nutrient regeneration to take place ( Deming, 2002 ). For at least a million years, microbial communities have survived in permafrost ( Vorobyova et al., 1997 ) and at the base of the Antarctic ice sheet ( Christner et al., 2014 ). Microbial activity has been shown to occur down to −20°C in Arctic sea ice, adding to the concept that liquid inclusions provide an adequate habitat for microbial life ( Junge et al., 2004 ). There are no reports of growth below −15°C ( Mykytczuk et al., 2013 ) however, microorganisms have been shown to survive in situ at −30°C and have been predicted to metabolize at −40°C ( Price and Sowers, 2004 ). It appears that the lower growth temperature is fixed by the freezing properties of the aqueous solutions outside and immediately adjacent to the cell.


1980 Cataclysmic Eruption

Magma began intruding into the Mount St. Helens edifice in the late winter and early spring of 1980. By May 18, the cryptodome (bulge) on the north flank had likely reached the point of instability, and was creeping more rapidly toward failure.

Annotated seismogram indicates the signals for a Low-Frequency (LF) volcanic earthquake, relative quiescence, and then harmonic tremor as the eruption of May 18, 1980 accelerated. Each horizontal line represents 15 minutes of time. (Public domain.)

Summary of Events

On May 18, 1980, a magnitude-5+ earthquake was accompanied by a debris avalanche, which in turn unloaded the confining pressure at the top of the volcano by removing the cryptodome. This abrupt pressure release allowed hot water in the system to flash to steam, which expanded explosively, initiating a hydrothermal blast directed laterally through the landslide scar. Because the upper portion of the volcano was removed, the pressure decreased on the system of magma beneath the volcano. A wave of decreasing pressure down the volcanic conduit to the subsurface magma reservoir, which then began to rise, form bubbles (degas), and erupt explosively, driving a 9-hour long Plinian eruption.

Steam-blast eruption from summit crater of Mount St. Helens. Aerial view, April 6, looking southwest, showing a roiling, gray-brown, ash-laden cloud that envelops and almost completely hides an initial fingerlike ash column, and an upper white cloud formed by atmospheric condensation of water vapor in the convectively rising top of the eruptive column. Image and caption taken from Professional Paper 1250 and not scanned from original slide. (Credit: Moore, James G.. Public domain.)

Precursory Activity

On March 16, 1980, the first sign of activity at Mount St. Helens occurred as a series of small earthquakes. On March 27, after hundreds of additional earthquakes, the volcano produced its first eruption in over 100 years. Steam explosions blasted a 60- to 75-m (200- to 250-ft) wide crater through the volcano's summit ice cap and covered the snow-clad southeast sector with dark ash.

Within a week the crater had grown to about 400 m (1,300 ft) in diameter and two giant crack systems crossed the entire summit area. Eruptions occurred on average from about 1 per hour in March to about 1 per day by April 22 when the first period of activity ceased. Small eruptions resumed on May 7 and continued to May 17. By that time, more than 10,000 earthquakeshad shaken the volcano and the north flank had grown outward about 140 m (450 ft) to form a prominent bulge. From the start of the eruption, the bulge grew outward—nearly horizontally—at consistent rates of about 2 m (6.5 ft) per day. Such dramatic deformationof the volcano was strong evidence that molten rock (magma) had risen high into the volcano. In fact, beneath the surficial bulge was a cryptodome that had intruded into the volcano's edifice, but had yet to erupt on the surface.

Debris Avalanche

With no immediate precursors, a magnitude 5.1 earthquake occurred at 8:32 a.m. on May 18, 1980 and was accompanied by a rapid series of events. At the same time as the earthquake, the volcano's northern bulge and summit slid away as a huge landslide—the largest debris avalanche on Earth in recorded history. A small, dark, ash-rich eruption plume rose directly from the base of the debris avalanche scarp, and another from the summit crater rose to about 200 m (650 ft) high. The debris avalanche swept around and up ridges to the north, but most of it turned westward as far as 23 km (14 mi) down the valley of the North Fork Toutle River and formed a hummocky deposit. The total avalanche volume is about 2.5 km 3 (3.3 billion cubic yards), equivalent to 1 million Olympic swimming pools.

A "bulge" developed on the north side of Mount St. Helens as magma pushed up within the peak. Angle and slope-distance measurements to the bulge indicated it was growing at a rate of up to five feet (1.5 meters) per day. By May 17, part of the volcano's north side had been pushed upwards and outwards over 450 feet (135 meters). (Lipman, Peter. Public domain.)

Bulge (right) and small crater, Mount St. Helens summit. Crater area dropped in relation to the summit, and bulge shows pronounced fracturing because of its increased expansion. View looking south. (Credit: Krimmel, Robert M.. Public domain.)

Lateral Blast

Blowdown of trees from the shock-wave of the directed (lateral) blast from the May 18, 1980 eruption of Mount St. Helens. Elk Rock is the peak with a singed area on the left.

(Credit: Topinka, Lyn. Public domain.)

The landslide removed Mount St. Helens' northern flank, including part of the cryptodome that had grown inside the volcano. The cryptodome was a very hot and highly pressurized body of magma. Its removal resulted in immediate depressurization of the volcano's magmatic system and triggered powerful eruptions that blasted laterally through the sliding debris and removed the upper 300 m (nearly 1,000 ft) of the cone. As this lateral blast of hot material overtook the debris avalanche it accelerated to at least 480 km per hr (300 mi per hr). Within a few minutes after onset, an eruption cloud of blast tephra began to rise from the former summit crater. Within less than 15 minutes it had reached a height of more than 24 km (15 mi or 80,000 ft).

The lateral blast devastated an area nearly 30 km (19 mi) from west to east and more than 20 km (12.5 mi) northward from the former summit. In an inner zone extending nearly 10 km (6 mi) from the summit, virtually no trees remained of what was once dense forest. Just beyond this area, all standing trees were blown to the ground, and at the blast's outer limit, the remaining trees were thoroughly seared. The 600 km 2 (230 mi 2 ) devastated area was blanketed by a deposit of hot debris carried by the blast.

Plinian eruption column from May 18, 1980 Mount St. Helens. Aerial view from the Southwest. (Credit: Krimmel, Robert. Public domain.)

Plinian Eruption

Removal of the cryptodome and flank exposed the conduit of Mount St. Helens, resulting in a release of pressure on the top of the volcano's plumbing system. This caused a depressurization wave to propagate down the conduit to the volcano's magma storage region, allowing the pent-up magma to expand upward toward the vent opening. Less than an hour after the start of the eruption, this loss of conduit pressure initiated a Plinian eruption that sent a massive tephra plumehigh into the atmosphere. Beginning just after noon, swift pyroclastic flows poured out of the crater at 80 - 130 km/hr (50 to 80 mi/hr) and spread as far as 8 km (5 mi) to the north creating the Pumice Plain.

The Plinian phase continued for 9 hours producing a high eruption column, numerous pyroclastic flows, and ash fall downwind of the eruption. Scientists estimate that the eruption reached its peak between 3:00 and 5:00 p.m. When the Plinian phase was over, a new northward opening summit amphitheater 1.9 x 2.9 km (1.2 x 1.8 mi) across was revealed.

Ash cloud from Mount St. Helens over Ephrata, Washington (230 km (145mi) downwind), after May 18, 1980 eruption. (copyright by Douglas Miller)

Over the course of the day, prevailing winds blew 520 million tons of ash eastward across the United States and caused complete darkness in Spokane, Washington, 400 km (250 mi) from the volcano. Major ash falls occurred as far away as central Montana, and ash fell visibly as far eastward as the Great Plains of the Central United States, more than 1,500 km (930 mi) away. The ash cloud spread across the U.S. in three days and circled the Earth in 15 days.

During the first few minutes of this eruption, parts of the blast cloud surged over the newly formed crater rim and down the west, south, and east sides of the volcano. The turbulently flowing hot rocks and gas quickly eroded and melted some of the snow and ice capping the volcano, creating surges of water that eroded and mixed with loose rock debris to form lahars. Several lahars poured down the volcano into river valleys, ripping trees from their roots and destroying roads and bridges.

The largest and most destructive lahar occurred in the North Fork Toutle and was formed by water (originally groundwater and melting blocks of glacier ice) escaping from inside the huge landslide deposit through most of the day. This powerful slurry eroded material from both the landslide deposit and channel of the North Fork Toutle River. Increased in size as it traveled downstream, the lahar destroyed bridges and homes, eventually flowing into the Cowlitz River. It reached maximum size at about midnight in the Cowlitz River, about 80 km (50 mi) downstream from the volcano.

Nearly 135 miles (220 kilometers) of river channels surrounding the volcano were affected by the lahars of May 18, 1980. A mudline left behind on trees shows depths reached by the mud. (Credit: Topinka, Lyn. Public domain.)


Endocrine Diseases of Pregnancy

Inhibition of thyroid hormone synthesis by thyroid gland: Iodine, sulfonylureas, lithium

Increase in thyroid-stimulating hormone (TSH): Iodine, cimetidine, dopamine agonists, lithium

Decrease in TSH: Glucocorticoids, dopamine agonists, somatostatin

Inhibition of thyroid hormone binding to TBG (thyroid-binding globulin): Phenytoin, diazepam, sulfonylureas, furosemide, salicylates

Inhibition of conversion of T4 to T3 in peripheral tissues (liver): Glucocorticoids, Propylthiouracil (PTU), ipodate, propranolol, amiodarone

Inhibition of gastrointestinal resorption of thyroid hormones: Cholestyramine, cholestipol, ferrous sulfate


Watch the video: Martin Nonstatic - Reflecting Glaciers 2021 (January 2022).